ENHANCED NODE B AND METHOD FOR RRC CONNECTION ESTABLISHMENT FOR SMALL DATA TRANSFERS

Abstract

Embodiments of an enhanced Node B (eNB) and method for RRC connection establishment for small-data transfers in a 3GPP LTE network are generally described herein. The eNB may receive a small-data RRC connection request message from user equipment (UE) that may include an establishment clause value indicating small-data traffic either with or without mobility. The eNB may send an initial UE setup request message to inform the mobility management entity (MME) that a small-data RRC connection is being established. The eNB may receive an acceptance message from the MME for the small-data RRC connection which may include a reduction of an RRC inactivity timer for fast connection release. The eNB may send an RRC connection reconfiguration message to the UE in response to receipt of the acceptance to establish the small-data RRC connection, the RRC connection reconfiguration message including a measurement information element (IE) when mobility is to be supported.

Description

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No. 14/140,932, filed Dec. 26, 2013, which claims priority under 35 USC 119(e) to U.S. Provisional Patent Application Ser. No. 61/808,597, filed Apr. 4, 2013, each of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments pertain to wireless communications. Some embodiments relate to small-data transfer in 3GPP LTE networks. Some embodiments relate to machine-type communications (MTC).

BACKGROUND

Small-data transmission is becoming an issue for wireless communication especially for 4G (e.g., LTE) radios due to the burden of control signaling overhead. Compared to 3G, 4G provides an always connected data mode where the user equipment (UE) has the IP address. Whenever a UE connects to an LTE network, a default (e.g., best effort) flow is assigned to the UE along with an IP address. Besides the connection between UE and an enhanced Node B (eNB), this IP connection requires bearer establishment between the eNB and the core network. Thus, setting up a connection requires a great deal of signaling overhead. This overhead is negligible when the amount of data exchanged such as in applications such as web browsing or file transfer is very large. But a lot of other applications, such as social networking apps like Facebook, Twitter and machine-type communication (MTC) applications (e.g., smart parking meters), the amount of data transferred may be very small (e.g., hundreds of bites) compared to the signaling overhead involved in setting up and tearing down the LTE connection.

Thus there are general needs for reducing the signaling overhead for frequent small-data transmissions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a portion of an end-to-end network architecture of LTE (long term evolution) network with various components of the network in accordance with some embodiments.

FIG. 2 illustrates an RRC connection establishment procedure;

FIG. 3 illustrates an RRC connection establishment procedure for small-data transfer in accordance with some embodiments; and

FIG. 4 illustrates a functional block diagram of a UE in accordance with some embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

FIG. 1 shows a portion of an end-to-end network architecture of an LTE (long term evolution) network with various components of the network in accordance with some embodiments. The network comprises a radio access network (RAN) (e.g., as depicted, the E-UTRAN or evolved universal terrestrial radio access network) and the core network 120 (e.g., shown as an evolved packet core (EPC)) coupled together through an S1 interface 115. For convenience and brevity sake, only a portion of the core network, as well as the RAN, is shown.

The core 120 includes mobility management entity (MME) 122, serving gateway (serving GW) 124, and packet data network gateway (PDN GW) 126. The RAN includes enhanced node B's (eNBs) 104 (which may operate as base stations) for communicating with user equipment (UE) 102. The eNBs 104 may include macro eNBs and low power (LP) eNBs.

The MME is similar in function to the control plane of legacy Serving GPRS Support Nodes (SGSN). It manages mobility aspects in access such as gateway selection and tracking area list management. The serving GW 124 terminates the interface toward the RAN, and routes data packets between the RAN and core network. In addition, it may be a local mobility anchor point for inter-eNB handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. The Serving GW and the MME may be implemented in one physical node or separate physical nodes. The PDN GW terminates an SGi interface toward the packet data network (PDN). It routes data packets between the EPC and the external PDN, and may be a key node for policy enforcement and charging data collection. It may also provide an anchor point for mobility with non-LTE accesses. The external PDN can be any kind of IP network, as well as an IP Multimedia Subsystem (IMS) domain. The PDN GW and the Serving GW may be implemented in one physical node or separated physical nodes.

The eNB (macro and micro) terminates the air interface protocol and is usually (if not always) the first point of contact for a UE 102. In some embodiments, an eNB may fulfill various logical functions for the RAN including but not limited to RNC (radio network controller functions) such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management.

The S1 interface is the interface that separates the RAN and the EPC. It is split into two parts: the S1-U, which carries traffic data between the eNB and the Serving GW, and the S1-MME, which is a signaling interface between the eNB and the MME. The X2 interface is the interface between eNBs (at least between most, as will be addressed below regarding micro eNBs). The X2 interface comprises two parts, the X2-C and X2-U. The X2-C is the control plane interface between eNBs, while the X2-U is the user plane interface between eNBs.

With cellular networks, LP cells are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with very dense phone usage, such as train stations. As used herein, the term low power (LP) eNB refers to any suitable relatively low power eNB for implementing a narrower cell (narrower than a macro cell) such as a femtocell, a picocell, or a micro cell. Femtocell eNBs are typically provided by a mobile network operator to its residential or enterprise customers. A femtocell is typically the size of a residential gateway or smaller and generally connects to the user's broadband line. Once plugged in, the femtocell connects to the mobile operator's mobile network and provides extra coverage in a range of typically 30 to 50 meters for residential femtocells. Thus, a LP eNB might be a femtocell eNB since it is coupled through the PDN GW 126. Similarly, a picocell is a wireless communication system typically covering a small area, such as in-building (offices, shopping malls, train stations, etc.), or more recently in-aircraft. A picocell eNB can generally connect through the X2 link to another eNB such as a macro eNB through its base station controller (BSC) functionality. Thus, LP eNB 106 could be implemented with a picocell eNB since it is coupled to a macro eNB via an X2 interface. Picocell eNBs or other LP eNBs for that matter) may incorporate some or all functionality of a macro eNB. In some cases, this may be referred to as an access point base station or enterprise femtocell.

As mentioned above, small-data transmission is becoming an issue for wireless communication due to the burden of control signaling overhead particularly since the IP connection conventionally requires bearer establishment between an eNB 104 and the core network 120. Setting up a connection in the conventional manner thus requires a great deal of signaling overhead. Embodiments disclosed herein provide for a reduction in the signaling overhead for small-data transmissions. In accordance with embodiments, an eNB 104 may be configured for small-data radio-resource control (RRC) connection establishment in a 3GPP LTE network (e.g., a E-UTRAN of FIG. 1). In these embodiments, the eNB 104 may receive a small-data RRC connection request message from a UE 102. The small-data RRC connection request message may include an establishment clause value indicating small-data traffic either with or without mobility. The eNB 104 may send an initial UE setup request message to inform the MME 122 that a small-data RRC connection is being established. The eNB 104 may indicate to the MME 122 whether or not the small-data RRC connection is to be established with mobility. The eNB 104 may also receive an acceptance message from the MME 122 for the small-data RRC connection. The acceptance may include a reduction of an RRC inactivity timer for faster connection release. The eNB 104 may send an RRC connection reconfiguration message to the UE 102 in response to receipt of the acceptance to establish the small-data RRC connection. The RRC connection reconfiguration message may include a measurement information element (IE) when mobility is to be supported. These embodiments may achieve a significant reduction in control plane overhead for setting up connections for small-data transfers. These embodiments are described in more detail below.

Some conventional techniques for small-data transfer have proposed to use purely control plane solutions whereby the UE does not have to establish any data bearers and thus save time and air interface resources in setting up of connections over the air interface. However, these control plane solutions are constrained in several ways. For example, the solutions involving sending data over the control plane can be used only for traffic being sent one way (i.e. either the UE sends data to the sender (i.e. mobile originated (MO) data) or the UE receives data from the sender (i.e. mobile terminated (MT) data), but not allowing both during the connection. Another constraint is the UE may be able to send only one IP packet during the connection. Some of these constraints arise due to the absence of the UE being allocated an IP address.

Embodiments disclosed herein may help minimize the control plane overhead of setting up connections specifically for small-data transfers. These embodiments can be applied to MTC and non-MTC devices and allow multiple TCP/IP packets to be exchanged between a UE 102 and a destination.

FIG. 2 illustrates an RRC connection establishment procedure. As mentioned above, there are several steps involved in setting up a connection over the air interface between the UE 102 and the eNB 104 and between the eNB 104 and the core network EPC 120. The messages may be exchanged between the UE 102 and the eNB 104 and some of the messages may be exchanged between eNB 104, the MME 122, the S-GW 124 and the PDN-GW 126. In accordance with embodiments, some changes may be made to the steps of FIG. 2 to help minimize the control plane overhead of setting up connections for small-data transfers.

When a UE 102 needs to send data from an idle state, the UE may follow the same steps from step 1 until however, in the RRC connection request, the UE may state that the establishment cause is to do a small-data transfer. Currently this clause does not exist. Secondly the UE 102 may indicate whether it needs mobility support during the transfer or not. This provides support for non-MTC devices which may need mobility support even for small-data transfers since the device may be moving at high speeds even when transferring small data.

In step 6, when the eNB 104 forwards the UE's attach request to the MME 122, the eNB 104 may also include the information regarding small-data transfer to the MME.

In step 7, the MME 122 may validate whether this particular UE 102 can be allowed to perform small-data transfers and may send an acceptance. The MME 122 may modify the RRC inactivity timer for this connection to a very small value (e.g., to use the network RTT value such as 250 ms instead of current average of 510 secs).

In step 8, depending on whether the UE 102 indicated a need mobility support, the eNB 104 may include information to perform measurement reporting to the UE 102. If no support is required, the eNB 104 does refrain from sending such information saving air interface resources. The UE 102 may then perform a data packet transfer once it is allocated its IP address. The eNB 104 may release the UE's connection after the shorter inactivity period lasting on average the end-to-end round trip time to ensure no further packets were expected during this connection.

FIG. 3 illustrates an RRC connection establishment procedure for small-data transfer in accordance with some embodiments. In accordance with embodiments, an eNB 104 may arranged for small-data RRC connection establishment. In these embodiments, the eNB 104 may receiving a small-data RRC connection request message 302 from a UE 102. The small-data RRC connection request message 302 may include an establishment clause value indicating small-data traffic either with or without mobility. In these embodiments, the eNB 104 may send an initial UE setup request message 306 to inform the MME 122 that a small-data RRC connection for the UE 102 is being established. The eNB 104 may indicate to the MME 122 whether or not the small-data RRC connection is to be established with mobility. In these embodiments, the eNB 104 may receive an acceptance message 308 from the MME 122 for the small-data RRC connection. The acceptance may include a reduction of an RRC inactivity timer 314 for fast connection release. In these embodiments, the eNB 104 may send an RRC connection reconfiguration message 310 to the UE 102 in response to receipt of the acceptance 308 to establish the small-data RRC connection. The RRC connection reconfiguration message 310 may include a measurement information element (IE) when mobility is to be supported.

In some embodiments, indicating whether or not the small-data RRC connection is being established with mobility is part of the initial UE setup request message 306.

In some embodiments, the eNB 104 may add a field to an attach request message 304 received from the UE 102 to generate the initial UE setup request message 306. The added field may indicate small data in a dedicated non-access spectrum (NAS) information element (IE). The attach request message 304 with the added field may be forwarded by the eNB 104 to the MME 122.

In some embodiments, the eNB 104 may communicate small-data packets 312 with the UE 102 over the established small-data RRC connection prior to expiration of the reduced RRC inactivity timer. The small-data packets 312 may have a predetermined maximum size for small-data transfer.

In some embodiments, the UE 102 may be machine-type communications (MTC) device. In some embodiments, the UE 102 is a mobile device including a smart phone. In some embodiments, the small-data RRC connection request message includes an establishment clause value indicating small-data traffic without mobility. In some embodiments, the small-data RRC connection request message includes an establishment clause value indicating small-data traffic with mobility. In some embodiments, the predetermined maximum size for small-data transfer is 1-Kbyte, although the scope of the embodiments is not limited in this respect.

In accordance with embodiments, new establishment cause values are provided in an RRC Connection Request message (“small-data traffic with mobility” and “small-data traffic with no mobility”). Furthermore, new mechanisms are provided for an eNB 104 to inform the MME 122 that the connection request is a small-data transfer. In the attach request message forwarded by the eNB to the MME 122, a field may be added to indicate small-data message in the dedicated Info NAS IE. The eNB 104 may indicate to the MME 122 that this is a small-data transfer and may also indicate whether mobility support is required or not on top of attach request NAS message. When the eNB 104 receives attach accept message, the eNB 104 may send a RRC Connection Reconfiguration message (no measurement IE, no mobility IE, depending on whether mobility support required or not). The MME 122 may also send an updated RRC inactivity timer value for fast connection release. If the core network 120 knows this is a small-data transfer connection, it may not retain the tunnel information between the S-GW 124 and the eNB 104 and between PDN-GW 126 and the S-GW 124 for long periods of time and may release bearer resources earlier as well.

In Table 1, the new RRC Connection request message with a new establishment cause is illustrated.

TABLE 1
Updated RRC Connection Request Message
-- ASN1START
RRCConnectionRequest ::=        SEQUENCE {
criticalExtensions              CHOICE {
rrcConnectionRequest-r8         RRCConnectionRequest-r8-IEs,
criticalExtensionsFuture        SEQUENCE { }
}
}
RRCConnectionRequest-r8-IEs ::= SEQUENCE {
ue-Identity                     InitialUE-Identity,
establishmentCause              EstablishmentCause,
spare                           BIT STRING (SIZE (1))
}
InitialUE-Identity ::=          CHOICE {
s-TMSI                          S-TMSI,
randomValue                     BIT STRING (SIZE (40))
}
EstablishmentCause ::=          ENUMERATED {
                                emergency, highPriorityAccess, mt-
                                Access, mo-Signalling,
                                mo-Data, delayTolerantAccess-v1020,
                                SmallDataTrafficwithMobilityv12,
SmallDataTrafficwithNoMobility-v12}
-- ASN1STOP

Embodiments disclosed here may be applicable to small-data transmissions for both MTC and non-MTC devices. Embodiments disclosed herein may allow sending multiple IP packets and also TCP/IP packets. Embodiments disclosed herein may be flexible for mobile and non-mobile devices. Embodiments disclosed herein may reduce the impact of measurement configuration for mobile devices, saving signaling overhead. Embodiments disclosed do not compromise security. Embodiments disclosed herein may save UE power by releasing the connection quickly, also saving network resources.

In some embodiments, the packets for small-data transfer are smaller in size (e.g. in the order of hundreds of bytes) with average packet size of 100 bits and may have a predetermined maximum size of 1 Kbyte, although the scope of the embodiments is not limited in this respect. In some embodiments, an eNB 104 may refrain from including an establishment clause value indicating small-data traffic for RRC connection requests that are not for small-data traffic.

FIG. 4 illustrates a functional block diagram of a UE in accordance with some embodiments. UE 400 may be suitable for use as UE 102 (FIG. 1) although other UE configurations may also be suitable. The UE 400 may include physical layer circuitry 402 for transmitting and receiving signals to and from eNBs 104 (FIG. 1) using one or more antennas 401. UE 400 may also include medium access control layer (MAC) circuitry 404 for controlling access to the wireless medium. UE 400 may also include processing circuitry 406 and memory 408 arranged to perform the operations described herein. The block diagram illustrated by FIG. 4 may also be functionally suitable for an eNB, such as eNB 104 (FIG. 1) although other configurations for an eNB may also be suitable. In some embodiments, the eNB may include network interface circuitry arranged to perform at least some of the operations described herein.

In some embodiments, the UE 400 may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other device that may receive and/or transmit information wirelessly. In some embodiments, the UE 400 may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

The one or more antennas 401 utilized by the UE 400 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some embodiments, instead of two or more antennas, a single antenna with multiple apertures may be used. In these embodiments, each aperture may be considered a separate antenna. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result between each of antennas and the antennas of a transmitting station. In some MIMO embodiments, the antennas may be separated by up to 1/10 of a wavelength or more.

Although the UE 400 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements.

Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer-readable storage medium, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage medium may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage medium may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. In these embodiments, one or more processors may be configured with the instructions to perform the operations described herein.

In some embodiments, the UE 400 may be configured to receive OFDM communication signals over a multicarrier communication channel in accordance with an OFDMA communication technique. The OFDM signals may comprise a plurality of orthogonal subcarriers. In some broadband multicarrier embodiments, eNBs may be part of a broadband wireless access (BWA) network communication network, such as a 3rd Generation Partnership Project (3GPP) Universal Terrestrial Radio Access Network (UTRAN) Long-Term-Evolution (LTE) or a Long-Term-Evolution (LTE) communication network, although the scope of the invention is not limited in this respect. In these broadband multicarrier embodiments, the UE 400 and the eNBs 104 (FIG. 1) may be configured to communicate in accordance with an orthogonal frequency division multiple access (OFDMA) technique.

In some LTE embodiments, the basic unit of the wireless resource is the Physical Resource Block (PRB). The PRB may comprise 12 sub-carriers in the frequency domain×0.5 ms in the time domain. The PRBs may be allocated in pairs (in the time domain). In these embodiments, the PRB may comprise a plurality of resource elements (REs). A RE may comprise one sub-carrier×one symbol.

Two types of reference signals may be transmitted by an eNB including demodulation reference signals (DM-RS), channel state information reference signals (CIS-RS) and/or a common reference signal (CRS). The DM-RS may be used by the UE for data demodulation. The reference signals may be transmitted in predetermined PRBs.

In some embodiments, the OFDMA technique may be either a frequency domain duplexing (FDD) technique that uses different uplink and downlink spectrum or a time-domain duplexing (TDD) technique that uses the same spectrum for uplink and downlink.

In some other embodiments, the UE 400 and the eNBs may be configured to communicate signals that were transmitted using one or more other modulation techniques such as spread spectrum modulation (e.g., direct sequence code division multiple access (DS-CDMA) and/or frequency hopping code division multiple access (FH-CDMA)), time-division multiplexing (TDM) modulation, and/or frequency-division multiplexing (FDM) modulation, although the scope of the embodiments is not limited in this respect.

In some LTE embodiments, the UE 400 may calculate several different feedback values which may be used to perform channel adaption for closed-loop spatial multiplexing transmission mode. These feedback values may include a channel-quality indicator (CQI), a rank indicator (RI) and a precoding matrix indicator (PMI). By the CQI, the transmitter selects one of several modulation alphabets and code rate combinations. The RI informs the transmitter about the number of useful transmission layers for the current MIMO channel, and the PMI indicates the codebook index of the precoding matrix (depending on the number of transmit antennas) that is applied at the transmitter. The code rate used by the eNB may be based on the CQI. The PMI may be a vector that is calculated by the UE and reported to the eNB. In some embodiments, the UE may transmit a physical uplink control channel (PUCCH) of format 2, 2a or 2b containing the CQI/PMI or RI.

In these embodiments, the CQI may be an indication of the downlink mobile radio channel quality as experienced by the UE 400. The CQI allows the UE 400 to propose to an eNB an optimum modulation scheme and coding rate to use for a given radio link quality so that the resulting transport block error rate would not exceed a certain value, such as 10%. In some embodiments, the UE 400 may report a wideband CQI value which refers to the channel quality of the system bandwidth. The UE 400 may also report a sub-band CQI value per sub-band of a certain number of resource blocks which may be configured by higher layers. The full set of sub-bands may cover the system bandwidth. In case of spatial multiplexing, a CQI per code word may be reported.

In some embodiments, the PMI may indicate an optimum precoding matrix to be used by the eNB 104 for a given radio condition. The PMI value refers to the codebook table. The network configures the number of resource blocks that are represented by a PMI report. In some embodiments, to cover the system bandwidth, multiple PMI reports may be provided. PMI reports may also be provided for closed loop spatial multiplexing, multi-user MIMO and closed-loop rank 1 precoding MIMO modes.

In some cooperating multipoint (CoMP) embodiments, the network may be configured for joint transmissions to a UE 400 in which two or more cooperating/coordinating points, such as remote-radio heads (RRHs) transmit jointly. In these embodiments, the joint transmissions may be MIMO transmissions and the cooperating points are configured to perform joint beamforming.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b) requiring an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

1. A method performed by an enhanced node B (eNB) for small-data radio-resource control (RRC) connection establishment in a 3GPP LTE network, the method comprising:

receiving a small-data RRC connection request message from user equipment (UE), the small-data RRC connection request message including an establishment clause value indicating small-data traffic either with or without mobility;

sending an initial UE setup request message to inform a mobility management entity (MME) that a small-data RRC connection for the UE is being established;

indicating to the MME whether or not the small-data RRC connection is to be established with mobility;

receiving an acceptance message from the MME for the small-data RRC connection, the acceptance message including a reduction of an RRC inactivity timer for fast connection release; and

sending an RRC connection reconfiguration message to the UE in response to receipt of the acceptance to establish the small-data RRC connection, the RRC connection reconfiguration message including a measurement information element (IE) when mobility is to be supported.